let notSure:any = 3
notSure = '1'
notSure = {}

let value:unknown 

value = true
value ='hello'
value = []
value = null


// unknown类型和any类型的区别：可以将any类型赋值给任意类型，导致ts的类型限定变成了js一样的弱类型，而unknown只能赋值给unknown类型